The present invention relates to a system and method of generating wet steam of known quality and splitting the generated wet steam into at least two streams of wet steam have substantially equal quality and injecting the wet steam under a controlled rate into separate wells used in the recovery of oil from a subterranean, viscous oil-containing formation.
Steam injection or steam flooding has gained substantial recognition in the art as a preferred method for recovering viscous or heavy oil from subterranean oil-containing formations. In one oil recovery process, steam is injected into one or more wells for a period of time, after which steam injection is terminated and oil is pumped to the surface of the earth through the same well or wells as were used for injecting the steam in the formation which is sometimes referred to as "push-pull" steam stimulation. In another recovery process using steam, the steam is injected into the formation via an injection well and passes through the formation displacing oil toward a spaced-apart production well from which oil is recovered.
These viscous oil recovery processes utilizing steam generally involve the use of a single steam generator and a plurality of wells for steam injection. The steam generated is preferably wet steam with sufficient liquid content to prohibit deposition of salts in the steam generating apparatus. The quality of the produced wet steam is a measure of the weight percent which is in the vapor phase. Thus, 80% quality steam means that 80% of the steam on the basis of weight is vapor with the remaining 20% being liquid phase.
When the flow of wet steam from a steam generator is split into two streams using a convention "Tee," the two streams will not have the same quality. The change in steam quality by splitting in known to be effected by the two-phase flow regime just ahead of the flow splitting. The flow may change from bubble flow to stratified flow to slug flow to annular flow as the liquid to vapor ratio changes from high to low. Since the heat content or enthalpy of the vapor phase portion of the steam is substantially higher than the liquid phase, the heat content of each stream is therefore different which makes it difficult to control and measure the amount of heat injected into the wells from a split stream.
In view of the foregoing discussion, it can be appreciated that there is a substantial, unfulfilled need for a method of splitting a stream of wet steam into two or more equal quality streams for injection into separate wells used in an oil recovery process.